Vehicular exhaust systems comprise an array of pipes which extend from the engine to a location where exhaust gases can be safely and conveniently released. The exhaust gases generally are very hot. As a result, a clearance often is specified between the exhaust system components and certain other parts of the vehicle to prevent heat related damage. The size of the required clearance depends on the temperature of the heated pipe and the characteristics of the adjacent parts of the vehicle.
Air gap pipes comprising an inner exhaust carrying pipe and an outer pipe spaced from the inner pipe have been employed in exhaust systems where specified clearances are difficult to attain and where heat related damage would otherwise be likely. The air gap between the inner and outer pipes provides a heat insulation which substantially eliminates or reduces the possibility of damage or hazards which can occur when the exhaust system is too close to adjacent structures.
Air gap pipes have been known for several years. However, until recently the manufacture of air gap pipes was extremely time-consuming and expensive. In particular, one prior art manufacturing technique for air gap pipes involved bending both the inner and outer pipes into complementary shapes. The outer pipe was then manually cut longitudinally in half, and the two longitudinal outer pipe halves were manually secured around the inner pipe. Another prior art manufacturing method involved placing a linear inner pipe concentrically within a linear outer pipe. A filler material with a low melting point was then placed in the annular space between the inner and outer pipes. The composite structure of the inner and outer pipes and the filler therebetween was then bent into the selected nonlinear shape. The entire assembly was then heated sufficiently to melt the filler material, and to enable the filler material to be poured from the annular space between the inner and outer pipes. Both of these prior art manufacturing methods were labor intensive, time-consuming and economically inefficient for all but small special orders.
Substantial structural and manufacturing improvements recently have been made in connection with air gap pipes. In particular, an efficient manufacturing method has been developed wherein the inner and outer pipes are bent into complementary nonlinear configurations. Supporting structures, such as inwardly directed dimples or cantilevered spring fingers then are formed in the outer pipe. The bent outer pipe is then cut longitudinally in half by two cooperating preprogrammed robotic cutting devices. The precisely cut outer pipe halves then are clamped around the inner pipe and are welded together to define the air gap pipe. The resulting product, the manufacturing method and certain manufacturing equipment are disclosed in U.S. Pat. No. 4,501,302 and U.S. Pat. No. 4,619,292, both of which issued to Jon W. Harwood, and in U.S. Pat. No. 4,712,295 which issued to Camille Peele, et al. These prior art patents are assigned to the assignee of the subject invention, and the disclosures of these patents are incorporated herein by reference.
The complex bending of the outer pipe for the air gap pipe system creates various localized stresses within the metal of the pipe. The entire uncut bent outer pipe is in a substantial state of equilibrium despite these localized stresses created during the bending process. However, the longitudinal cut placed in the outer pipe often will upset this equilibrium causing each longitudinal half of the pipe to move relative to its initial alignment. Furthermore, the respective longitudinal halves generally will not move symmetrically relative to one another. In fact, opposed longitudinal portions of a pipe may move in opposite directions after the bent pipe is severed. To exacerbate this problem, pipes are known to exhibit different metallurgical characteristics along their length and from one pipe to the next. Thus, the exact pattern of dimensional changes in the longitudinal halves of the pipe can not be predicted prior to cutting the pipe.
This tendency of the longitudinal halves of the pipe to alter their shapes has caused substantial manufacturing problems. In particular, the outer pipe halves will not align with one another when they are placed around the inner pipe for purposes of rewelding.
U.S. Pat. No. 4,712,295 shows and describes a unique clamping apparatus which addresses the problem of misalignment of the respective outer pipe halves and enables an efficient flow of work from the rapid robotic cutting devices shown therein. In particular, the clamp apparatus shown in U.S. Pat. No. 4,712,295 includes a first support having a recess dimensioned to receive the bottom half of the pipe. A gripping means is operative to accurately engage two opposed edge locations on the bottom half of the outer pipe to urge the bottom half of the pipe securely into the recess despite the possibility of minor alignment variations along the length of the pipe. The inner pipe is then placed within the bottom longitudinal half of the outer pipe, and the top longitudinal half is loosely positioned over the bottom longitudinal half of the outer pipe. A second support with a recess to engage the top half of the outer pipe is then actuated to urge the top longitudinal half of the outer pipe into proper alignment with the bottom longitudinal half. Thus, the gripping means and the second support correct any misalignment that may have existed in either the bottom or top longitudinal halves of the outer pipe. A plurality of such clamping devices typically would be disposed along the length of the pipe to ensure proper alignment of the entire pipe. The outer pipe halves would then be rewelded to one another to complete the manufacturing process of the air gap pipe.
Although the clamp apparatus shown in U.S. Pat. No. 4,712,295 is extremely effective, it is desirable to provide a clamp apparatus offering greater operational efficiency and greater versatility. It is also desired to provide a clamp apparatus that is mechanically and functionally simpler.
In view of the above, it is an object of the subject invention to provide a clamp apparatus for more efficiently clamping opposed longitudinal halves of a pipe into proper alignment with one another.
It is another object of the subject invention to provide an apparatus for clamping longitudinal halves of a pipe securely together despite dimensional or geometric variations between various pipe sections.
It is a further object of the subject invention to provide an apparatus for clamping opposed longitudinal halves of a pipe together with only a single source of power.
An additional object of the subject invention is to provide a clamping apparatus with interchangeable clamping jaws and interchangeable supports to accomodate pipes of substantially different dimensions.